Abstract: Providing a viewfinder optical system capable of obtaining given magnification and a given eyepoint, suitable for an SLR digital camera and an SLR camera, an optical apparatus equipped therewith, and a method for expanding observation. The viewfinder optical system M including an eyepiece optical system 15 for observing a real image of an object formed by an objective lens 11 through an erecting image forming member 14, the eyepiece optical system 15 consisting of, in order from the object along an optical axis, a double concave negative lens, a double convex positive lens, a lens, and a meniscus lens having a convex surface facing the object; an optical apparatus 10 equipped therewith; and a method for expanding observation.

Abstract: A zoom lens having an optical element for deflecting an optical path includes, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; a fourth lens group having positive refractive power; and a fifth lens group having negative refractive power. The third lens group has a plurality of lenses, and the following conditional expressions 1.00<PL/fW<1.75 and 0.30<PL/fT<0.45 are satisfied, where PL denotes an optical path length of the optical element for deflecting the optical path, fW denotes a focal length of the zoom lens in a wide angle end state, and fT denotes a focal length of the zoom lens in a telephoto end state.

Abstract: A zoom lens having an optical element for deflecting an optical path includes, in order from an object: a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; a fourth lens group having positive refractive power; and a fifth lens group having negative refractive power. The third lens group has a plurality of lenses, and the following conditional expressions 1.00<PL/fW<1.75 and 0.30<PL/fT<0.45 are satisfied, where PL denotes an optical path length of the optical element for deflecting the optical path, fW denotes a focal length of the zoom lens in a wide angle end state, and fT denotes a focal length of the zoom lens in a telephoto end state.

Abstract: An object is to provide an ultra-compact zoom lens system suitable for a video camera and a electronic still camera using a solid-state imaging device and the like with securing high optical performance. The zoom lens system includes, in order from an object along the optical axis, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and at least one lens group having positive refractive power. The first lens group is fixed upon zooming from a wide-angle end state to an telephoto end state and focusing. A plurality of lens groups except the first lens group are moved upon zooming from the wide-angle end state to the telephoto end state, respectively. A plurality of lens groups except the first lens group G1 are moved upon focusing, respectively. Given conditional expressions are satisfied.

Abstract: Providing an ultra-compact zoom lens system having a vibration reduction function, suitable for a compact optical device using a solid-state imaging device. The system includes, in order from an object, a first lens group having positive power and a bending member for bending the optical path by about 90°, a second lens group having negative power, a third lens group having positive power, and a fourth lens group having positive power. Upon zooming from a wide-angle end state to a telephoto end state, the first and third lens groups are fixed with respect to an image plane, the second lens group is moved to the image, and the fourth lens group is moved at first to the object and then to the image plane. An image blur on the image plane caused by a camera shake is corrected by moving the third lens group perpendicularly to the optical axis.

Abstract: The common zoom optical system is provided that is almost commonly used in a plurality of zoom lenses as a component and that is capable of suppressing fluctuation in aberrations and deviation in the position of the image plane, wherein the common zoom optical system is almost commonly used in a plurality of zoom lenses as a component, and when zooming from a wide-angle end state of a plurality of the zoom lenses composed by use of the common zoom optical system to a telephoto end state thereof, a moving path of the common zoom optical system differs for each zoom lens.

Abstract: In a zoom lens ZL1 having a plurality of lens groups G1 to G2 which are disposed in order from an object, where a refractive index average value of the lens components which constitute the zoom lens ZL1 is defined as ndav and a refractive index average value of the lens components which constitute the first lens group G1 which is disposed to closest to the object among the plurality of lens groups G1 to G2 is defined as ndGlav, the zoom lens ZL1 is constituted to satisfy the conditional expression ndav?1.80 and to satisfy the conditional expression ndGlav?1.85.

Abstract: Providing a viewfinder optical system capable of obtaining given magnification and a given eyepoint, suitable for an SLR digital camera and an SLR camera, an optical apparatus equipped therewith, and a method for expanding observation. The viewfinder optical system M including an eyepiece optical system 15 for observing a real image of an object formed by an objective lens 11 through an erecting image forming member 14, the eyepiece optical system 15 consisting of, in order from the object along an optical axis, a double concave negative lens, a double convex positive lens, a lens, and a meniscus lens having a convex surface facing the object; an optical apparatus 10 equipped therewith; and a method for expanding observation.

Abstract: Providing an ultra-compact zoom lens system having a vibration reduction function, suitable for a compact optical device using a solid-state imaging device. The system includes, in order from an object, a first lens group having positive power and a bending member for bending the optical path by about 90°, a second lens group having negative power, a third lens group having positive power, and a fourth lens group having positive power. Upon zooming from a wide-angle end state to a telephoto end state, the first and third lens groups are fixed with respect to an image plane, the second lens group is moved to the image, and the fourth lens group is moved at first to the object and then to the image plane. An image blur on the image plane caused by a camera shake is corrected by moving the third lens group perpendicularly to the optical axis.

Abstract: An object is to provide an ultra-compact zoom lens system suitable for a video camera and a electronic still camera using a solid-state imaging device and the like with securing high optical performance. The zoom lens system includes, in order from an object along the optical axis, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and at least one lens group having positive refractive power. The first lens group is fixed upon zooming from a wide-angle end state to an telephoto end state and focusing. A plurality of lens groups except the first lens group are moved upon zooming from the wide-angle end state to the telephoto end state, respectively. A plurality of lens groups except the first lens group G1 are moved upon focusing, respectively. Given conditional expressions are satisfied.

Abstract: An object is to provide an ultra-compact zoom lens system suitable for a video camera and a electronic still camera using a solid-state imaging device and the like with securing high optical performance. The zoom lens system includes, in order from an object along the optical axis, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and at least one lens group having positive refractive power. The first lens group is fixed upon zooming from a wide-angle end state to an telephoto end state and focusing. A plurality of lens groups except the first lens group are moved upon zooming from the wide-angle end state to the telephoto end state, respectively. A plurality of lens groups except the first lens group G1 are moved upon focusing, respectively. Given conditional expressions are satisfied.

Abstract: The object is to provide a zoom lens system having a zoom ratio of 2.5 or more, compactness and high optical performance, applicable to a plurality of imaging devices with different image heights. According to one aspect of the present invention, a zoom lens system applicable to a plurality of imaging devices having different image heights with each other by partially sharing zooming trajectories without changing an optical element of the zoom lens system.

Abstract: The common zoom optical system is provided that is almost commonly used in a plurality of zoom lenses as a component and that is capable of suppressing fluctuation in aberrations and deviation in the position of the image plane, wherein the common zoom optical system is almost commonly used in a plurality of zoom lenses as a component, and when zooming from a wide-angle end state of a plurality of the zoom lenses composed by use of the common zoom optical system to a telephoto end state thereof, a moving path of the common zoom optical system differs for each zoom lens.

Abstract: An object is to provide an ultra-compact zoom lens system suitable for a video camera and a electronic still camera using a solid-state imaging device and the like with securing high optical performance. The zoom lens system includes, in order from an object along the optical axis, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having positive refractive power, and at least one lens group having positive refractive power. The first lens group is fixed upon zooming from a wide-angle end state to an telephoto end state and focusing. A plurality of lens groups except the first lens group are moved upon zooming from the wide-angle end state to the telephoto end state, respectively. A plurality of lens groups except the first lens group G1 are moved upon focusing, respectively. Given conditional expressions are satisfied.

Abstract: The object is to provide a zoom lens system having a zoom ratio of 2.5 or more, compactness and high optical performance, applicable to a plurality of imaging devices with different image heights. According to one aspect of the present invention, a zoom lens system applicable to a plurality of imaging devices having different image heights with each other by partially sharing zooming trajectories without changing an optical element of the zoom lens system.